The present invention relates to mechanisms for wrapping large cylindrical bales while in the bale-forming chamber of a large round baler, and more specifically relates to such mechanisms for placing net over the edges of such bales.
In popular use today are large round balers equipped with net wrapping mechanisms which place a web of plastic net about the circumference of a bale prior to the bale being discharged onto the ground. U.S. Pat. No. 4,969,315, granted to Ardueser et al. on Nov. 13, 1990, discloses such a device mounted to the discharge gate of a large round baler having an expansible baling chamber. Most of these mechanisms do not consistently place net up to the edges at the ends of the bales and this results in spoilage occurring at the ends of the bale and also in the bales having a somewhat poor appearance.
It has been recognized that the above-mentioned drawbacks associated with current net wrapping mechanisms could be avoided by also wrapping the corners and outer end portions of the bale (see U.S. Pat. No. 4,917,008 granted to Wildenberg et al. on Apr. 17, 1990). In order for the edge zones of the material to fold about the end edges of the bale and cover and extend a short distance on the end faces of the bale, this patent teaches that outer borders of the net should be made with elastic filaments. The making of net with different longitudinal elasticity across its width is somewhat inefficient and the usage of such net in some delivery systems is not entirely satisfactory since it is desirable to maintain a certain tension in the net as it is being wrapped around a bale in order to obtain a tight wrap without rupturing the material, and the control of tension in net having different elasticity across its width poses design difficulties.
U.S. Pat. No. 5,104,714, granted to Leiber et al. on Apr. 14, 1992 discloses a net wrap material constructed from thin ribbons of thermoplastic material, developed for wrapping pallet loads or agricultural bales, which exhibits a uniform, high degree of elasticity across its width when stretched in the longitudinal direction. The preferred characteristics of the knitted net material is to have an elongation at break of more than about 60%, an elastic limit of more than about 6% and an elasticity of more than 15% when elongated more than 40%.